Hi Dave I retro fitted mine with bits off ebay for about £30. Spacesaver was an additional £35.
https://www.ebay.co.uk/itm/Volvo-XC9...kAAOSw50Vdv0eq
Reading this it does look like it changed which seems odd.
When you remove the winch blanking plate bolts it looks like you have to remove the rearmost seats to get it out and install the winch.
This is not the case even though you will see some info to say that it is!
All you need to do is remove a couple of the bolts from the seat rail with everything in situ and you can get the plate out and the winch in.
One point to remember is that if your XC has the twin exhausts ie one either side, I'm led to believe that a spare wheel will not fit.
If you do eventually get a second hand winch and want a photo of the bracket and bolts to remove, drop me a PM and I'll sort it